The present invention relates generally to hemostasis valves and, more particularly, to hemostasis valves for positioning and manipulating intravascular catheters.
It is well known in angiography and cardiac catheterization to use an introducer sheath assembly to provide a passageway to the lumen of a blood vessel through which a catheter can be inserted or removed without blood loss. The introducer sheath assembly typically comprises a body having a valve assembly, the body being coupled to or extending into a flexible cannula which is inserted into the blood vessel cannula usually using a needle, guidewire and dilator. See U.S. Pat. No. 4,000,739. The valve assembly is designed to seal around the catheter when it is in place and to seal off the passage within the introducer sheath assembly when the catheter is withdrawn.
In many procedures followed today it is necessary to use more than one catheter and to exchange one catheter for another which is already in place in the vessel. In such a procedure with the guidewire still in the vessel, the catheter in the body is withdrawn over the guidewire. The guidewire is left within the body through the introducer cannula and introducer valve assembly. The new catheter is inserted through the introducer into the body over the existing guidewire.
In valves having an elastic membrane having a hole therein to accommodate and seal against the catheter, while the guidewire is in place after the first catheter is removed and before the second catheter is inserted, leakage of blood through the introducer valve often occurs since the guidewire has a smaller diameter than the catheter. This is, of course, undesirable.
Other valves for sealing the catheter without using a hole in the membrane and which will accommodate a range of catheter and guidewire diameters are in use but often such designs result in higher frictional forces about the guidewire or catheter being manipulated making it more difficult for the physicians.
It is desirable, therefore, to provide a valve which will provide a good seal when a catheter is present, or with a guidewire alone or when neither the guidewire nor the catheter is present, and which provides relative ease of manipulation of the catheter or guidewire when in use.